1. Field of the Invention
The invention relates to a seal assembly for aviation rotor bearings. More specifically, the invention relates to a swashplate seal assembly for protection of rotorcraft bearings associated with a rotor shaft unit.
2. Description of the Related Art
Conventional rotorcrafts such as helicopters and tilt wing aircraft having propulsion systems which are adjustable in positioning angle, typically include rotor shaft units having one or more rotor bearing ring assembles which are accompanied by swashplate assemblies. Examples of conventional helicopter swashplate assemblies are provided in U.S. Pat. No. 4,804,315, issued to Ferris et al., U.S. Pat. No. 5,071,319, issued to McCafferty, and U.S. Pat. No. 5,074,494, issued to Doolin et al. A large number of maintenance issues arise in the swashplate assembly and the rotor bearing ring assembly due to wear in all parts, binding of seals, metal fatigue in the rotor bearing ring, and bearing spalling leading to abnormal wear of bearings and associated components. One method to reduce the frequency of inspections for the swashplate assembly and rotor bearing ring is to provide ample lubrication of the parts, although such lubrication rapidly deteriorates due to exposure to environmental contaminants such as dust, pollen and moisture. Frequent cleaning of a rotor shaft assembly outer surfaces and shaft seals leads to water seeping down the rotor shaft to the rotor bearing ring if a swashplate seal assembly is in a state of degradation due to exposure to contaminants and/or frequent disassembly during inspections of the rotor bearing ring.
The U.S. Army utilizes a system of frequent inspections of swashplate assemblies as determined by the frequency of problems observed during field operations of helicopters. Due to the logistics of operating a helicopter for military use, any potential failure of parts as indicated by inspection findings and partial failures is consider highly significant due to a risk of loss of life when helicopter seal assemblies fail. During the prior decade of helicopter operations, a significant number of problems relating to helicopter swashplate assemblies have occurred due to stress fractures in rotor bearing cages and/or bearing components contact leading to abnormal bearing component wear which leads to catastrophic results. In order to prevent catastrophic results, frequent and extensive rotor shaft, rotor bearing cage, and swashplate seal assembly inspections are accomplished, with resulting loss of helicopter flight time.
A need exists for an improved swashplate seal assembly for a helicopter rotor shaft in order to minimize the exposure of contaminants to the rotor bearing unit of a rotor shaft assembly. An additional need exists for an improved swashplate seal assembly and method of use providing for reduced frequencies of inspections and a more efficient inspection of the swashplate seal assembly and rotor bearing unit.